1. Field of the Invention
The present invention relates to an electronic system and, more particularly, to an electronic system in which a multipower source type is used as a power source.
2. Related Background Art
In such systems, a plurality of batteries are used as a plurality of power sources. In this case, the above system detects electric power consumption of the battery itself by a voltage drop state of the battery and to inform the user of the time to exchange the battery on the basis of the detected electric power consumption state. Even in the case where a multipower source (dry batteries, alkaline batteries, AC adapters, etc.) type is used as power sources of the system having such functions, the detection value of the voltage when the above functions are made operative is constant.
On the other hand, in the case of using various kinds of batteries as power sources, if the battery shapes are similar, although the various kinds of batteries can be inserted into battery boxes, the kind of battery inserted in the battery box cannot be discriminated from the outside.
Therefore, the case of using dry batteries (manganese batteries) as power sources and the case of using nickel-cadmium batteries as power sources will be first considered. A voltage (V.sub.B) of battery gradually drops in dependence on its electric power consumption state. FIGS. 19A and 19B show voltage drop states. In both diagrams, a state of a change in each voltage drop when a load fluctuation is small is shown. For instance, in an apparatus such as a typewriter or the like for making a printer operative, since the loads when a motor is rotating and when the motor stops differ, widely the voltage V.sub.B gradually changes while increasing and decreasing. Particularly, in the case of the manganese battery shown in FIG. 19A, since its internal resistance is high, a tendency of the fluctuation is typical. However, when a voltage average value per certain unit time is calculated, a voltage drop phenomenon as shown in FIG. 19A appears. In FIG. 19A, point E denotes a voltage at which the driving of the apparatus as a load can be compensated. Since the internal resistances of the manganese battery and nickel-cadmium battery actually differ, the voltage drops in the case of extracting the same load differ and the performances of the batteries are also variable, so that the positions of the E points shown in the diagrams are not always coincident. However, in the specification, it is assumed that the positions of points E coincide for convenience of explanation. When the changes in the voltages V.sub.B shown in FIGS. 19A and 19B are compared, generally, it can be said that there is a feature such that although the nickel-cadmium battery holds an almost predetermined voltage level near the initial voltage value until a certain time as compared with that of the manganese battery, the voltage suddenly drops after that.
In the electronic system using two kinds of batteries as mentioned above, if weak battery voltages (hereinafter, referred to as "WB") in the case of informing the user of the battery changing timings by the voltage V.sub.B of the power source are set to the same value, there are the following drawbacks.
For instance, when WB=WB.sub.1, in the case of the nickel-cadmium battery shown in FIG. 19B, the battery life is short to a certain extent at the point of WB.sub.1 and the time of t.sub.3 until point E remains. On the other hand, in the case of the manganese battery shown in FIG. 19A, the time t.sub.1 remains at the point of WB.sub.1 until point E and an enough long life still remains. When setting to WB=WB.sub.1 as mentioned above, although it is ideal for the nickel-cadmium battery, in such a range, the manganese battery can be still sufficiently useful and the timing of point WB.sub.1 is improper to generate an alarm to the user.
Then, in the case of setting to WB=WB.sub.2, in the manganese battery shown in FIG. 19A, the time t.sub.2 remains until point E and the remaining life is shortened to a certain degree. On the other hand, in the nickel-cadmium battery shown in FIG. 19B, the very short time of t.sub.4 remains until point E. As mentioned above, when setting WB=WB.sub.2, although such a point is proper for the manganese battery, only an extremely short time of t.sub.4 remains for the nickel-cadmium battery. Even if an alarm is generated to the user at the time point of WB.sub.2, there is not sufficient time until point E. It is considered that the absence of a sufficient time range causes a step-out of the motor at the time point exceeding point E if the user continuously uses the motor without becoming aware of the alarm during the operation, for instance, when the user is printing by means of the typewriter or the like.
As mentioned above, in the case of measuring the power voltage drop and setting the point of WB, if power sources of different characteristics are used, when the user intends to set the value of WB to a predetermined single point independently of the kinds of power sources, unreasonableness occurs that is disadvantageous to the user of the system.
On the other hand, when the voltages are detected at the same timing irrespective of the kinds of batteries, if the characteristics are matched with the characteristics of the voltage drop of one battery, they do not coincide with the characteristics of the voltage drop of the other battery. Thus, there occurs an inconvenience such that a possibility in which the voltage detecting point of the other battery becomes improper is high.
Further, in the case of displaying a residual amount of the battery capacity step by step, in order to calculate a percentage of electric power consumption of the battery on the basis of the battery voltage in accordance with the kind of battery, it is impossible to discriminate those percentage values by the same voltage value in both batteries. On the other hand, since the voltage drop phenomena of the batteries change depending on a load, it is impossible to measure the electric power consumption of the batteries with the same timing.
On the other hand, when the kind of internal battery cannot be discriminated from the outside, if the battery enters the state of WB, the battery cover must be opened every time and the kind of battery inserted in the battery box must be checked by the eyes. For instance, when the battery enters the WB state, as a method of recovering the power source, in the case of the nickel-cadmium battery, it is necessary to charge it by an AC power source. On the other hand, in the case of a dry battery, a new battery is necessary. In such a case, since the kind of internal battery cannot be discriminated from the outside, the user cannot immediately determine by which method the power source should be recovered.